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The production and consumption of coffee generates large amounts of waste which, if released into the environment, could cause unacceptable pollution. The search for alternatives for the use of these waste materials, namely coffee silver skin (CSS) and spent coffee grounds (SCG), is of great importance from an environmental and economic point of view. In this context, the present study was conducted to evaluate the use of CSS and SCG as mineral sources in order to strengthen their status as novel foods, which is currently not recognised. With the aim of validating the content of metals and metalloids in CSS and SCG, a comparative study of green and roasted coffee was also conducted. The results of the HR-ICP-MS analyses showed that coffee and coffee by-products contain high levels of macro essential elements: K (2387–35 993 mg/kg), Mg (1263–5298 mg/kg) and Na (82.6–170 mg/kg). Among the essential trace elements, Fe predominated with amounts between 41.8 and 728 mg/kg. The essential elements in the ultra-trace range (Mo, Cr, Co and Se) are found in amounts between 0.02 and 2.42 mg/kg. The content of toxic elements (Pb, As, Cd and Sn) is in the range of 0.01–0.25 mg/kg, which is below the maximum levels set by the EU Commission for these elements in foodstuff. However, the levels of Rb, Ba, Sr, Ti and Al are high, and range from 2.33 to 764 mg/kg. Considering the high content of essential elements in CSSs that are useful for daily human needs, the potential use of CSS should be encouraged. On the other hand, in order to meet the requirements for the use of novel foods, monitoring of potentially toxic elements must be carried out. [ABSTRACT FROM AUTHOR]

Seeking food-derived antioxidants and inhibitors of α-glucosidase and α-amylase has been recognized as an effective way for managing diabetes. Coffee silver skin (CSS) is rich in phenolic compounds, which may be potential agents as antioxidants and for α-glucosidase and α-amylase inhibition. But whether phenolics in different forms show similar bioactivity remains unknown. In this study, phenolic compounds in CSS were extracted as free phenolics (FPs), esterified phenolics (EPs), and bound phenolics (BPs). The phenolic profiles and antioxidant activities of them were investigated. Their inhibitory effects on α-glucosidase and α-amylase were analyzed, and the inhibitory mechanisms were elucidated by molecular docking and molecular dynamic simulation. Results showed that FPs exhibited the best antioxidant ability and inhibitory effects on α-glucosidase and α-amylase. A total of 17 compounds were identified in FPs with 3-caffeoylquinic acid, 4-feruloylquinic acid, and dicaffeoylquinic acids as the dominant ones. Typical phenolics in FPs could bind to α-glucosidase and α-amylase through hydrogen bonds and form hydrophobic interaction with several key amino acid residues. In addition, 3,4-dicaffeoylquinic acid and 3-caffeoylquinic acid might be the principal components that account for the inhibitory effect of FPs on α-glucosidase. The results of this study may provide some scientific support for CSS utilization as a health-beneficial component in functional food development for type 2 diabetes mellitus management. [ABSTRACT FROM AUTHOR]

This research developed a bio-based polymer composite using polylactic acid (PLA) and agro-industrial residues from coffee by-products (without chemical modification and the use of coupling agents or stabilizers). Agro-industrial residues, such as spent coffee ground (SCG) and coffee silver skin (CSS) as filler, were added into the PLA matrix in different percentages by weight, from 0.5 to 10 wt%. The bio-composites were prepared using solvent-cast films and were characterized by various techniques, including FT-IR, TGA, DSC, XRD, SEM and mechanical tests. Bio-composites' formation was verified using FT-IR and SEM; the material showed good interfacial interaction, with percentages between 3 and 5 wt%. XRD and DSC determined the percentage crystallinity in the bio-composites. SEM found that the bio-composites form crystals, showing their limits after mechanical testing. The bio-composites exhibited enhanced thermal and mechanical properties compared to neat PLA.These bio-based composites show great potential for a wide range of applications in the food industry, including disposable and single-use materials, as well as food packaging. Moreover, their use can significantly contribute to the global demand for eco-friendly materials.

Seeking food-derived antioxidants and inhibitors of α-glucosidase and α-amylase has been recognized as an effective way for managing diabetes. Coffee silver skin (CSS) is rich in phenolic compounds, which may be potential agents as antioxidants and for α-glucosidase and α-amylase inhibition. But whether phenolics in different forms show similar bioactivity remains unknown. In this study, phenolic compounds in CSS were extracted as free phenolics (FPs), esterified phenolics (EPs), and bound phenolics (BPs). The phenolic profiles and antioxidant activities of them were investigated. Their inhibitory effects on α-glucosidase and α-amylase were analyzed, and the inhibitory mechanisms were elucidated by molecular docking and molecular dynamic simulation. Results showed that FPs exhibited the best antioxidant ability and inhibitory effects on α-glucosidase and α-amylase. A total of 17 compounds were identified in FPs with 3-caffeoylquinic acid, 4-feruloylquinic acid, and dicaffeoylquinic acids as the dominant ones. Typical phenolics in FPs could bind to α-glucosidase and α-amylase through hydrogen bonds and form hydrophobic interaction with several key amino acid residues. In addition, 3,4-dicaffeoylquinic acid and 3-caffeoylquinic acid might be the principal components that account for the inhibitory effect of FPs on α-glucosidase. The results of this study may provide some scientific support for CSS utilization as a health-beneficial component in functional food development for type 2 diabetes mellitus management.

The development of fully renewable and biodegradable composites for short-term applications was pursued by combining a compatibilized poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) (60:40 wt:wt) blend with coffee silver skin (CSS), an industrial byproduct from coffee processing. An epoxy-based reactive agent (Joncryl ADR-4468) was added as a compatibilizer. CSS was incorporated at 5, 10, and 20 wt% in the blend both in the as-received state and after a simple thermal treatment in boiling water, which was performed to mitigate the negative impact of this filler on the rheological and mechanical properties of the blend. The CSS treatment effectively increased the filler degradation temperature of 30–40 °C, enabling stable melt processing of the composites. It also improved filler–matrix adhesion, resulting in enhanced impact properties (up to +172% increase in impact energy compared to the untreated filler). Therefore, treated CSS demonstrated potential as an effective green reinforcement for PLA/PBSA blends for rigid packaging applications. Future works will focus on studying suitable surface modification of CSS to further increase the interfacial interaction and the tensile quasi-static properties, to fully exploit the capabilities of this renewable material toward the development of eco-friendly composites. [ABSTRACT FROM AUTHOR]

ABSTRACTThe development of sound-absorbing panels which used coffee-silver-skin (CS) and melamine-urea-formaldehyde (MUF) as a composite board was studied. In this experiment, the objective was to examine the impact on the sound absorption coefficient (SAC) when incorporating wood husk into the composite board, specifically in the cases of CS (100%) and CS (90%) mixed with wood husk (10%), while simultaneously reducing the amount of MUF adhesive and adding corn starch (25%). It was observed that as the MUF content of the board decreased to 75%, the sound absorption coefficient average (SAA) were found to be 0.59 and 0.62 for the middle- and high-frequency ranges, respectively. For the frequency range higher than 3.15 kHz, the maximum SAC value of sample boards was 0.91 and the noise reduction coefficient (NRC) value was 0.47. While, the result showed the maximum SAC and the NRC value of sample boards were 0.93 and 0.48, respectively above the frequency range higher than 1.25 kHz for decreasing the MUF adhesive of board to 50%. Similarly, the addition of wood husk and corn starch mixed to CS could increase the SAA value of sample boards in the middle- and high-frequency range.

The development of sound-absorbing panels which used coffee-silver-skin (CS) and melamine-urea-formaldehyde (MUF) as a composite board was studied. In this experiment, the objective was to examine the impact on the sound absorption coefficient (SAC) when incorporating wood husk into the composite board, specifically in the cases of CS (100%) and CS (90%) mixed with wood husk (10%), while simultaneously reducing the amount of MUF adhesive and adding corn starch (25%). It was observed that as the MUF content of the board decreased to 75%, the sound absorption coefficient average (SAA) were found to be 0.59 and 0.62 for the middle- and high-frequency ranges, respectively. For the frequency range higher than 3.15 kHz, the maximum SAC value of sample boards was 0.91 and the noise reduction coefficient (NRC) value was 0.47. While, the result showed the maximum SAC and the NRC value of sample boards were 0.93 and 0.48, respectively above the frequency range higher than 1.25 kHz for decreasing the MUF adhesive of board to 50%. Similarly, the addition of wood husk and corn starch mixed to CS could increase the SAA value of sample boards in the middle- and high-frequency range. [ABSTRACT FROM AUTHOR]

The development of fully renewable and biodegradable composites for short-term applications was pursued by combining a compatibilized poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) (60:40 wt:wt) blend with coffee silver skin (CSS), an industrial byproduct from coffee processing. An epoxy-based reactive agent (Joncryl ADR-4468) was added as a compatibilizer. CSS was incorporated at 5, 10, and 20 wt% in the blend both in the as-received state and after a simple thermal treatment in boiling water, which was performed to mitigate the negative impact of this filler on the rheological and mechanical properties of the blend. The CSS treatment effectively increased the filler degradation temperature of 30–40 °C, enabling stable melt processing of the composites. It also improved filler–matrix adhesion, resulting in enhanced impact properties (up to +172% increase in impact energy compared to the untreated filler). Therefore, treated CSS demonstrated potential as an effective green reinforcement for PLA/PBSA blends for rigid packaging applications. Future works will focus on studying suitable surface modification of CSS to further increase the interfacial interaction and the tensile quasi-static properties, to fully exploit the capabilities of this renewable material toward the development of eco-friendly composites.

This research developed a bio-based polymer composite using polylactic acid (PLA) and agro-industrial residues from coffee by-products (without chemical modification and the use of coupling agents or stabilizers). Agro-industrial residues, such as spent coffee ground (SCG) and coffee silver skin (CSS) as filler, were added into the PLA matrix in different percentages by weight, from 0.5 to 10 wt%. The bio-composites were prepared using solvent-cast films and were characterized by various techniques, including FT-IR, TGA, DSC, XRD, SEM and mechanical tests. Bio-composites' formation was verified using FT-IR and SEM; the material showed good interfacial interaction, with percentages between 3 and 5 wt%. XRD and DSC determined the percentage crystallinity in the bio-composites. SEM found that the bio-composites form crystals, showing their limits after mechanical testing. The bio-composites exhibited enhanced thermal and mechanical properties compared to neat PLA. These bio-based composites show great potential for a wide range of applications in the food industry, including disposable and single-use materials, as well as food packaging. Moreover, their use can significantly contribute to the global demand for eco-friendly materials. [Display omitted] • A bio-based polymer composite was developed using PLA and agro-industrial residues from coffee by-products. • As filler, spent coffee ground (SCG) and coffee silver skin (CSS) were added to the PLA matrix. • SCG and CSS as fillers were used without chemical pretreatment and coupling agents. • The bio-composites exhibited enhanced thermal and mechanical properties compared to neat PLA. • The new bio-based plastic can be used for food packaging applications, promoting sustainable materials. [ABSTRACT FROM AUTHOR]

Roasted coffee silver skin is a coffee by-product, the uses of which are currently limited, e.g., as fertilizer, for energy production, or animal feed. Due to a low content of fat and carbohydrates combined with a high content of fiber, polyphenols and proteins, roasted silver skin is a valuable possible food ingredient. Potential applications include partial flour replacement in bakery products, as antioxidant and providing protein or fiber sources in sports or functional foods. As no relevant consumption of isolated silver skin occurred before 1997 in the European Union (EU), it was classified as a novel food in need of premarketing approval. Novel food applications must meet legal requirements for compositional and toxicological information. This review presents information on silver skin composition and toxicological studies. Several in vitro studies and subchronic in vivo studies are available with negative results, not suggesting a need for further studies on carcinogenic effects, reproduction, or chronic toxicity. All available studies so far concluded that no toxic effects of silver skin were found or are to be expected. For a novel food application in the EU, further in vitro studies on mutagenic potential may be needed to close a formal data gap. [ABSTRACT FROM AUTHOR]

The study objective was to assess the effect of "power ultrasound (US)" at different intervals on the techno-functional properties of food co-product ingredients, apple pomace (AP) and coffee silverskin (CSS). The primary focus was on the characterisation of techno-functional properties of ingredients, which are necessary for suitable application in meat products, such as water absorption capacity (WAC), oil absorption capacity (OAC), colour evaluation, particle size and rheology. Improvement of techno-functional properties such as WAC, OAC and particle size of ingredients can improve the water-holding capacity, cook loss and emulsion stability of processed meat products thereby enhancing their eating quality. Aqueous solutions (10% w/v) of the individual ingredients were treated with US (20 kHz, 250 W) for 15 and 30 min and freeze-dried. Results of US-treated AP showed that there was a rise in WAC (P < 0.05) and OAC (P < 0.05), whereas in CSS, there was an increase in WAC and OAC, but were not significant enough to prove the effect of US. Proximate analysis showed that US decreased moisture (P < 0.05) in both ingredients. Results showed that there was an increase (P < 0.01) in the protein (%) of CSS but no significant difference in protein (%) in AP samples. No significant difference was observed in fat, ash, fibre and apparent viscosity for both US-treated ingredients. Colour difference (ΔE) showed that US produced visible colour changes in both AP and CSS. Particle-size analysis showed there was an increase (P < 0.01) in D (3, 2) values of both ingredients. The results indicate that US treatment has beneficial impacts on the techno-functional properties of food co-products, AP and CSS powders. [ABSTRACT FROM AUTHOR]

Particulate composites based on poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) biopolymers have been formulated. Silver skin (SSK), the by‐product derived from the roasting of coffee beans, has been milled to micrometric size and added up to a 30 wt% of loading, without any previous treatment. The dynamic mechanical properties of the composites have been investigated, as well as the stability toward UV and IR radiation. The filler improves some mechanical properties such as the elastic modulus (E′) mostly in PBS. Photoaging experiments demonstrate that SSK, due to its polyphenols content and antioxidant activity, is able to protect both PLA and PBS from UV degradation, highlighting an added value of SSK waste‐based composites. [ABSTRACT FROM AUTHOR]

Roasted coffee silver skin is a coffee by-product, the uses of which are currently limited, e.g., as fertilizer, for energy production, or animal feed. Due to a low content of fat and carbohydrates combined with a high content of fiber, polyphenols and proteins, roasted silver skin is a valuable possible food ingredient. Potential applications include partial flour replacement in bakery products, as antioxidant and providing protein or fiber sources in sports or functional foods. As no relevant consumption of isolated silver skin occurred before 1997 in the European Union (EU), it was classified as a novel food in need of premarketing approval. Novel food applications must meet legal requirements for compositional and toxicological information. This review presents information on silver skin composition and toxicological studies. Several in vitro studies and subchronic in vivo studies are available with negative results, not suggesting a need for further studies on carcinogenic effects, reproduction, or chronic toxicity. All available studies so far concluded that no toxic effects of silver skin were found or are to be expected. For a novel food application in the EU, further in vitro studies on mutagenic potential may be needed to close a formal data gap.

The coffee plant Coffea spp. offers much more than the well-known drink made from the roasted coffee bean. During its cultivation and production, a wide variety of by-products are accrued, most of which are currently unused, thermally recycled, or used as animal feed. The modern, ecologically oriented society attaches great importance to waste reduction, so it makes sense to not dispose of the by-products of coffee production but to bring them into the value chain. The aim of this presentation is to provide an updated overview of novel coffee products in the food sector and their current legal classification in the European Union (EU). Coffee flowers, leaves, cascara, coffee cherry spirit, silver skin, and coffee wood are among the materials considered in this article. Some of these products may have, at least, an indirect history of consumption in Europe (silver skin), while others have already been used as traditional foods in non-EU-member countries (coffee leaves, flowers, cascara, and coffee cherry spirit). Of these, coffee leaf tea and cascara have already been approved by the European Commission. Following a consultation with EU member states, spent coffee grounds were determined as being not novel. For the other products, toxicity and/or safety data need to be gathered to further advance novel food applications.

Coffee silver skin is produced in large amounts as a by-product during the coffee roasting process. In this study, coffee silver skin of the species Coffea arabica L. and Coffea canephora Pierre ex A. Froehner as well as silver skin pellets produced in the coffee industry were characterized with respect to both nutritional value and potential heat-induced contaminants. Enzymatic-gravimetric/chromatographic determination of the dietary fiber content showed values ranging from 59 to 67 g/100 g with a comparably high portion of soluble fiber, whereas low molecular weight soluble fiber was not detected. Compositional and methylation analysis indicated the presence of cellulose and xylans in the insoluble dietary fiber fraction, whereas pectic polysaccharides dominate the soluble dietary fiber fraction. The protein content as determined by the Kjeldahl method was in the range of 18 to 22 g/100 g, and all essential amino acids were present in coffee silver skin; whereas fat contents were low, high ash contents were determined. Elemental analysis by inductively coupled plasma mass spectrometry (ICP-MS) showed the presence of macroelements in large amounts, whereas toxic mineral elements were only detected in trace amounts or being absent. Acrylamide was quantified with levels of 24–161 µg/kg. Although 5-hydroxymethylfurfural was detected, its concentration was below the limit of determination. Furfuryl alcohol was not detected.

The development of fully renewable and biodegradable composites for short-term applications was pursued by combining a compatibilized poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) (60:40 wt:wt) blend with coffee silver skin (CSS), an industrial byproduct from coffee processing. An epoxy-based reactive agent (Joncryl ADR-4468) was added as a compatibilizer. CSS was incorporated at 5, 10, and 20 wt% in the blend both in the as-received state and after a simple thermal treatment in boiling water, which was performed to mitigate the negative impact of this filler on the rheological and mechanical properties of the blend. The CSS treatment effectively increased the filler degradation temperature of 30-40 °C, enabling stable melt processing of the composites. It also improved filler-matrix adhesion, resulting in enhanced impact properties (up to +172% increase in impact energy compared to the untreated filler). Therefore, treated CSS demonstrated potential as an effective green reinforcement for PLA/PBSA blends for rigid packaging applications. Future works will focus on studying suitable surface modification of CSS to further increase the interfacial interaction and the tensile quasi-static properties, to fully exploit the capabilities of this renewable material toward the development of eco-friendly composites.

Many beneficial effects of coffee have been ascribed to the presence of chlorogenic acids. For this reason, some green coffee bean decaffeinated extracts claiming several beneficial effects are actually on the market as either nutraceuticals or food supplements. Herein, we compared the polyphenol content of green coffee beans, roasted coffee, spent coffee and silver-skins. The phenolic fraction of all samples was assessed using both colorimetric and HPLC-UV approaches, performing a full detailed identification and quantification of the phenols by liquid chromatography high-resolution mass spectrometry. Furthermore, we also evaluated the antioxidant activity of the different extracts. Notably, silver-skin extract possesses a superimposable profile compared to green coffee beans extract, and such a profile was unaltered by silver-skin decaffeination. This study reveals the perspective of using decaffeinated silver-skins as a low-cost raw material for the preparation of caffeine-free, chlorogenic acid-based food supplements and nutraceuticals.

Many beneficial effects of coffee have been ascribed to the presence of chlorogenic acids. For this reason, some green coffee bean decaffeinated extracts claiming several beneficial effects are actually on the market as either nutraceuticals or food supplements. Herein, we compared the polyphenol content of green coffee beans, roasted coffee, spent coffee and silver-skins. The phenolic fraction of all samples was assessed using both colorimetric and HPLC-UV approaches, performing a full detailed identification and quantification of the phenols by liquid chromatography high-resolution mass spectrometry. Furthermore, we also evaluated the antioxidant activity of the different extracts. Notably, silver-skin extract possesses a superimposable profile compared to green coffee beans extract, and such a profile was unaltered by silver-skin decaffeination. This study reveals the perspective of using decaffeinated silver-skins as a low-cost raw material for the preparation of caffeine-free, chlorogenic acid-based food supplements and nutraceuticals. [ABSTRACT FROM AUTHOR]

This paper presents the sound absorption performance of natural fiber composites developed from chrome shave (CS) and coffee silver skin (CSS). Twelve test samples of thickness 30 mm and 50 mm were fabricated with different fiber sizes and fiber ratios and by maintaining the density of the samples by 150 kg/m3. Normal incidence sound absorption coefficient spectra were measured in an impedance tube. Absorption coefficient spectra were predicted using the Johnson-Allard-Champoux (JCA) model using best fit values of tortuosity and the two characteristic lengths together with measured values of porosity and flow resistivity. The results revealed that the CS-CSS composite had average absorption coefficient of 0.95 above 1 kHz for a thickness of 30 mm and 50 mm. 'The predictions and data are in good agreement up to 6 kHz. [ABSTRACT FROM AUTHOR]

Coffee silver skin is produced in large amounts as a by-product during the coffee roasting process. In this study, coffee silver skin of the species Coffea arabica L. and Coffea canephora Pierre ex A. Froehner as well as silver skin pellets produced in the coffee industry were characterized with respect to both nutritional value and potential heat-induced contaminants. Enzymatic-gravimetric/chromatographic determination of the dietary fiber content showed values ranging from 59 to 67 g/100 g with a comparably high portion of soluble fiber, whereas low molecular weight soluble fiber was not detected. Compositional and methylation analysis indicated the presence of cellulose and xylans in the insoluble dietary fiber fraction, whereas pectic polysaccharides dominate the soluble dietary fiber fraction. The protein content as determined by the Kjeldahl method was in the range of 18 to 22 g/100 g, and all essential amino acids were present in coffee silver skin; whereas fat contents were low, high ash contents were determined. Elemental analysis by inductively coupled plasma mass spectrometry (ICP-MS) showed the presence of macroelements in large amounts, whereas toxic mineral elements were only detected in trace amounts or being absent. Acrylamide was quantified with levels of 24–161 µg/kg. Although 5-hydroxymethylfurfural was detected, its concentration was below the limit of determination. Furfuryl alcohol was not detected. [ABSTRACT FROM AUTHOR]

• Kinetic analysis of Coffee Silver Skin pyrolysis is studied through deconvolution. • Activation energy is calculated by Ozawa-Flynn-Wall and Starink kinetic methods. • Reaction mechanisms of pseudo-components are evaluated by employing master plots method. • Pyrolysis of pseudo lignin is in two-step reaction process. • Thermodynamic parameters (ΔH, ΔG, ΔS) are also calculated. Biomass is a fundamental renewable resource to develop sustainable energy conversion systems with low environmental impact. The design of biomass pyrolysis, gasification, and combustion facilities requires a particular attention at kinetic aspects. A coffee production residue such as coffee silver skin, which is the main product of the coffee roasting industry, is very suitable for thermochemical conversion, being already dry and containing compounds like the ochratoxin which does not allow its use in the production of biochemicals. In this work, thermal degradation tests of coffee silver skin are made under inert conditions at various heating rates (5, 7, 10, 15 °C/min) and a proper kinetic model was considered in order to quantify the activation energy (E α). The variation of E α with the conversion rate (α) was higher than 30%, showing that the process is kinetically complex and the kinetics cannot be described by a single-step model, according to the International Confederation on Thermal Analysis and Calorimetry. For this reason, a multi-step model and an analytical approach were used. This involves the deconvolution of the individual peaks of each pseudo-component from the overall differential kinetic curves, followed by the application of a model free-isoconversional method to the separated decomposition steps. The determination of the reaction mechanism f(α) of each sub-component (pseudo-cellulose P-CL, pseudo-hemicellulose P-HC, and pseudo-lignin P-LG) was performed by using both the Master-Plots method and the Energy Compensation Effect. The pre-exponential factor, the enthalpy and the Gibbs free energy were also evaluated in order to investigate the pyrolysis characteristics. A second order model mechanism was obtained for P-CL and P-HC, whereas no clear mechanism was found for P-LG when α > 0.5. [ABSTRACT FROM AUTHOR]

The coffee plant Coffea spp. offers much more than the well-known drink made from the roasted coffee bean. During its cultivation and production, a wide variety of by-products are accrued, most of which are currently unused, thermally recycled, or used as animal feed. The aim of this review is to provide an overview of novel coffee products in the food sector and their current legal classification in the European Union (EU). For this purpose, we have reviewed the literature on the composition and safety of coffee flowers, leaves, pulp, husk, parchment, green coffee, silver skin, and spent coffee grounds. Some of these products have a history of consumption in Europe (green coffee), while others have already been used as traditional food in non-EU-member countries (coffee leaves, notification currently pending), or an application for authorization as novel food has already been submitted (husks, flour from spent coffee grounds). For the other products, toxicity and/or safety data appear to be lacking, necessitating further studies to fulfill the requirements of novel food applications. [ABSTRACT FROM AUTHOR]